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C. Melody Carswell Cindy H. Lio Martina I. Klein Duncan Clarke Stephen Strup 《Applied ergonomics》2010,42(1):138-145
Introduction
Subjective workload measures are usually administered in a visual-manual format, either electronically or by paper and pencil. However, vocal responses to spoken queries may sometimes be preferable, for example when experimental manipulations require continuous manual responding or when participants have certain sensory/motor impairments. In the present study, we evaluated the acceptability of the hands-free administration of two subjective workload questionnaires - the NASA Task Load Index (NASA-TLX) and the Multiple Resources Questionnaire (MRQ) - in a surgical training environment where manual responding is often constrained.Method
Sixty-four undergraduates performed fifteen 90-s trials of laparoscopic training tasks (five replications of 3 tasks - cannulation, ring transfer, and rope manipulation). Half of the participants provided workload ratings using a traditional paper-and-pencil version of the NASA-TLX and MRQ; the remainder used a vocal (hands-free) version of the questionnaires. A follow-up experiment extended the evaluation of the hands-free version to actual medical students in a Minimally Invasive Surgery (MIS) training facility.Results
The NASA-TLX was scored in 2 ways - (1) the traditional procedure using participant-specific weights to combine its 6 subscales, and (2) a simplified procedure - the NASA Raw Task Load Index (NASA-RTLX) - using the unweighted mean of the subscale scores. Comparison of the scores obtained from the hands-free and written administration conditions yielded coefficients of equivalence of r = 0.85 (NASA-TLX) and r = 0.81 (NASA-RTLX). Equivalence estimates for the individual subscales ranged from r = 0.78 (“mental demand”) to r = 0.31 (“effort”). Both administration formats and scoring methods were equally sensitive to task and repetition effects. For the MRQ, the coefficient of equivalence for the hands-free and written versions was r = 0.96 when tested on undergraduates. However, the sensitivity of the hands-free MRQ to task demands (ηpartial2 = 0.138) was substantially less than that for the written version (ηpartial2 = 0.252). This potential shortcoming of the hands-free MRQ did not seem to generalize to medical students who showed robust task effects when using the hands-free MRQ (ηpartial2 = 0.396). A detailed analysis of the MRQ subscales also revealed differences that may be attributable to a “spillover” effect in which participants’ judgments about the demands of completing the questionnaires contaminated their judgments about the primary surgical training tasks.Conclusion
Vocal versions of the NASA-TLX are acceptable alternatives to standard written formats when researchers wish to obtain global workload estimates. However, care should be used when interpreting the individual subscales if the object is to make comparisons between studies or conditions that use different administration modalities. For the MRQ, the vocal version was less sensitive to experimental manipulations than its written counterpart; however, when medical students rather than undergraduates used the vocal version, the instrument’s sensitivity increased well beyond that obtained with any other combination of administration modality and instrument in this study. Thus, the vocal version of the MRQ may be an acceptable workload assessment technique for selected populations, and it may even be a suitable substitute for the NASA-TLX. 相似文献3.
OBJECTIVE: To determine whose naive judgments of consumer product usability are more accurate--those of younger or older adults. Accuracy is here defined as judgments compatible with results from performance-based usability tests. BACKGROUND: Older adults may be better able to predict usability problems than younger adults, making them particularly good participants in studies contributing to the user-centered design of products. This advantage, if present, may stem from older adults' motivation for more usable products or from their experience adapting their own environments to meet their changing physical, cognitive, and sensory needs. METHOD: Sixty older participants (ages 65-75 years) and 60 younger ones (ages 18-22 years) evaluated illustrations of consumer products on specific criteria (e.g., readability, learnability, or error rates). They either rated a single design for each product or ranked six alternative designs. They also explained their choices, indicated which features were most critical for usability, and selected usability-enhancing modifications. RESULTS: Although there was no reliable age difference in the amount of usability information provided in the open-ended explanations, older adults were more accurate at ranking alternative designs, selecting the most usability-critical features, and selecting usability-enhancing modifications (all ps < .05). CONCLUSION: The usability judgments of older adults are more accurate than those of younger adults when these judgments are solicited in a fixed-alternative, but not open-ended, format. APPLICATION: Because older adults are more discerning about potential product usability problems, they may be particularly valuable as research participants in early-stage design research (prior to the availability of working prototypes). 相似文献
4.
The major challenges of designing multicast traffic control protocols for a combined wired/wireless network are the varying
transmission characteristics (bandwidth, error, and propagation delay) of the wireless and wired media, and the different,
possibly conflicting frame rate requests from multiple sources. To address these issues, in this paper we design and evaluate
new unicast and multicast guaranteed frame rate (GFR) schemes for supporting TCP/IP traffic over a combined wired/wireless
ATM network. We first propose a new, flexible weighted buffer management, and a frame‐based virtual spacing (VS) mechanism
implementing weighted fair queueing. The unicast GFR scheme is based on the integration of the new weighted buffer management,
and either cell‐based or frame‐based VS. It is then extended to support multicast GFR flows. The multicast scheme presented
in this paper is the first multicast GFR scheme appeared in the literature. These schemes are carefully evaluated over several
network configuration, supporting heterogeneous TCP/IP traffic with various frame rates. Simulation results show that the
new schemes guarantee the minimum rates requested, provide excellent fairness, and achieve reasonably high efficiency. The
new schemes may be extended to provide differentiated service in both IP and mobile IP frame work.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
Effect of Bimodal Grain Size Distribution on the Strain Hardening Behavior of a Medium-Entropy Alloy
The evolution of strain hardening behavior of the Fe_(50)(CoCrMnNi)_(50) medium-entropy alloy as a function of the fraction of recrystallized microstructure and the grain size was studied using the Hollomon and Ludwigson equations.The specimens under study were partially recrystallized,fully recrystallized with ultrafine-grained microstructure,and fully recrystallized with coarse grains.The yield strength decreases steadily as the fraction of recry stallized micro structure and grain size increases due to the recovery process and the Hall-Petch effect.Interestingly,the bimodal grain distribution was found to have a significant impact on strain hardening during plastic deformation.For instance,the highest ultimate tensile strength was exhibited by a 0.97 μm specimen,which was observed to contain a bimodal grain distribution.Furthermore,using the Ludwigson equation,the effect of the bimodal grain distribution was established from the behavior of K_2 and n1 curves.These curves tend to show very high values in the specimens with a bimodal grain distribution compared to those that show a homogenous grain distribution.Additionally,the bimodal grain distribution contributes to the extensive L(u|")ders strain observed in the 0.97 μm specimen,which induces a significant deviation of the Hollomon equation at lower strains. 相似文献
6.
Melody L. Carter rew L. Gillen Kylie Olufson Eric R. Vance 《Journal of the American Ceramic Society》2009,92(5):1112-1117
Hot isostatically pressed tailored hollandite waste forms were used to demonstrate the immobilization of Cs and Sr are separable from spent nuclear fuel, as well as Ba and Rb. Four hollandite formulations were investigated, two samples with ∼12 wt% waste loading (on an oxide basis) and two with ∼18 wt% waste loading. Two of the samples were Al-substituted and the other two contained Mg. The hollandite in the Al-substituted samples contained all the waste cations, as designed, but this was not the case in the Mg-substituted samples. The hollandite in the Mg-substituted samples did not contain all the waste cations, with ∼50% of the Sr forming SrTiO3 as a secondary phase. This resulted in waste forms that were not as durable, with respect to Cs, as their Al counterparts. The formation of SrTiO3 had little effect on the Sr release rates and was not detrimental to the Mg-substituted hollandite waste form. For the Al-substituted samples, the MCC-1 normalized release rates were <0.06 g·(m2 ·day)−1 at 0–28 days for all elements, while the Cs release rates remained at 2.0 g·(m2 ·day)−1 at 0–28 days for the Mg-substituted samples. 相似文献
7.
8.
David P. Melody 《Polymer International》1989,21(2):175-179
Room temperature curing adhesives and sealants, defined here as those which cure without a mixing process under the influence of substrates or environmentally available reagents such as daylight, oxygen or moisture, include polyurethane, silicone, anaerobic adhesives, cyanoacrylate and certain acrylic types. Advances in cure chemistry, built-in adhesion promotion, and in formulating techniques have created the scope for significant new properties within all the mentioned systems. In addition, development of resins having two (or more) different functionalities, which respond to substrate and or atmospheric cure agents, has created the potential to achieve new advanced performance levels. Examples of these include compositions which give light curing through acrylic functions while having RTV (room temperature vulcanising) silicone resin chemistry polymerising under the influence of atmospheric moisture. The properties can be tailored by molecular design, formulation and choice of cure accelerators. 相似文献
9.
The gases evolved during activation of a sulfated zirconia prepared by impregnation with chloroplatinic acid have been followed
using mass spectrometry and infrared spectrometry. When the sample is heated in either helium or in air, the halogen is lost
from the catalyst as HCl and Cl2. Heating the sample in hydrogen results in the loss of the halogen as HCl, and only traces
as Cl2. The loss of halogen occurs over a wide temperature range (200-900°C). The data are consistent with the chloroplatinic
acid being converted by loss of halide with the formation of Pt0.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
Temporal variation of pharmaceuticals in an urban and agriculturally influenced stream 总被引:1,自引:0,他引:1
Pharmaceuticals have become ubiquitous in the aquatic environment. Previous studies consistently demonstrate the prevalence of pharmaceuticals in freshwater but we do not yet know how concentrations vary over time within a given system. Two sites in central Indiana with varying land use in the surrounding watershed (suburban and agricultural) were sampled monthly for pharmaceutical concentrations and stream physiochemical parameters. Sediment samples were also collected at each sampling event for measurement of δ15N natural abundance and sediment organic content. Across sites and sampling events, twelve pharmaceuticals were detected including acetaminophen, caffeine, carbamazepine, cotinine, N,N-diethyl-meta-toluamide (DEET), gemfibrozil, ibuprofen, sulfadimethoxine, sulfamethazine, sulfamethoxazole, triclosan, and trimethoprim. Sulfathiazole, lincomycin, and tylosin were not detected at either site at any time. The agriculturally-influenced site had comparable pharmaceutical concentrations to the urban-influenced site. In general, pharmaceutical concentrations increased during winter at both sites and decreased during spring and summer. Multiple regression analyses indicated that water column dissolved oxygen, the number of days since precipitation, and solar radiation influenced total pharmaceutical concentration in the urban-influenced site; whereas pH, chlorophyll a concentration, and total amount of rainfall in the previous 10 days influenced total pharmaceutical concentrations in the agriculturally-influenced site. Pharmaceutical concentrations were not correlated with sediment δ15N across or within sites. However, sediment in the urban-influenced site had higher mean δ15N signatures relative to sediment in the agriculturally-influenced site. These data indicate pharmaceuticals are persistent in aquatic ecosystems influenced by both agricultural and suburban activity. Pharmaceuticals are designed to have a physiological effect; therefore, it is likely that they may also influence aquatic organisms, potentially threatening freshwater ecosystem health. 相似文献